[vsnet-grb-info 20729] GRB 180620B: Swift/UVOT Detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  22827
SUBJECT: GRB 180620B: Swift/UVOT Detection
DATE:    18/06/23 11:44:09 GMT
FROM:    Alice Breeveld at MSSL-UCL  <a.breeveld at ucl.ac.uk>

A. A. Breeveld (UCL-MSSL), P. A. Evans (U. Leicester) and M. De Pasquale 
(U. Instanbul) report on behalf of the Swift/UVOT team:

The Swift/UVOT began settled observations of the field of GRB 180620B 92 
s after the BAT trigger (Evans et al., GCN Circ. 22807).
A source consistent with the enhanced XRT position (Beardmore et al., 
GCN Circ. 22814) and the Grond position (Schweyer and Schady, GCN Circ. 
22819), and also detected by Izzo et al. (GCN Circ. 22823) is detected 
in the initial UVOT exposures in all filters except uvw2. The 
non-detection in the uvw2 filter is consistent with the redshift of 1.12 
(Izzo et al. GCN Circ. 22823).

Preliminary detections and 3-sigma upper limits using the UVOT 
photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for 
the early exposures are:

Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white               92          242          147         18.06 ± 0.08
v                  634          826           39         17.41 ± 0.22
b                  559          579           20         17.56 ± 0.18
u                  304          554          246         17.40 ± 0.09
uvw1              9950        18219         1394         20.17 ± 0.2
uvm2              6563        16382          804         20.6 ± 0.3
uvw2              4256         4443          183         > 19.7

The magnitudes in the table are not corrected for the Galactic 
extinction due to the reddening of E(B-V) = 0.01 in the direction of the 
burst (Schlegel et al. 1998).